1. Field of the Disclosure
Embodiments disclosed herein generally relate to methods and assemblies that include a valve ball used to start and stop fluid flow. More specifically, embodiments disclosed herein relate to a valve assembly having a valve ball with multiple moveable seats to seal against fluid flow from the upstream and/or the downstream direction.
2. Background Art
The use of ball valves to start and stop the flow of fluids is well known in the art. Ball valves typically include a valve ball that is located between two seats in the middle of a passage. The valve ball has a through hole, and can be rotated between two positions. U.S. Pat. No. 5,246,203, issued to McKnight et al. (“McKnight”), incorporated by reference in its entirety, discloses an oilfield valve that incorporates a ball valve mechanism. The mechanics of a typical ball valve mechanism are demonstrated in the McKnight patent.
In a first position, as demonstrated in FIG. 1A, the through hole of the valve ball will align with the passage of the pipe or drill string. This position will generally allow complete and undisrupted fluid flow through the passage. The valve ball may then be rotated from this position into a second position, as demonstrated in FIG. 1B, to be misaligned with the passage of the pipe, thereby disrupting fluid flow. Each of the seats surrounding the valve ball, one upper seat and one lower seat, seal against the valve ball, not allowing flow between the valve ball and the seat. Thus, the valve ball, coupled with the two seats sealing against the valve ball, may stop fluid flow through the pipe passage when the valve ball is positioned in the closed position to misalign with the through hole passage by having the seats seal up against the valve ball. In FIG. 1B, a seal is made between the seats, 101 and 102, and the valve ball 105 to completely prohibit flow through the passage. The valve ball has the ability to seal against the seats to be effective against even the highest of pressures, allowing the arrangement to be used as a ball valve.
One issue with this type of ball valve arrangement is that when the valve ball 105 is in the second position, blocking flow through the passage, as seen in FIG. 1B, the valve ball 105 may not be able to effectively seal against the fluid flow, such as both in the upstream and downstream direction. For example, debris comes between the valve ball 105 and the seat 102, only sealing on the downstream seat 101 may be achieved. In such an example, if a fluid force is applied from the downstream direction, the debris may cause the valve to be unable to effectively seal between the valve ball 105 and the seat 102, thereby resulting in a leakage through the ball valve arrangement.
Further, because the valve ball 105 is usually fixed in all directions, except for rotating between an open and closed position, the seats 101 and 102 must be perfectly aligned with the valve ball 105 to ensure proper sealing engagement between the seats 101 and 102 and the valve ball 105. If the valve ball 105 shifts in any direction, such as towards either side with respect to the seats 101 and 102, then one or both of the seats 101 and 102 may lose effective sealing engagement with the valve ball 105.
For example, FIGS. 2A and 2B show a valve assembly having a seat 201 and a valve ball 205 disposed adjacent to each other with respect to an axis 200 of the valve assembly. In FIG. 2A, the seat 201 and the valve ball 205 are aligned with each other to ensure proper sealing engagement therebetween. However, in FIG. 2B, the valve ball 205 has shifted with respect to the seat 201 and the axis 200 such that the seat 201 and the valve ball 205 have lost proper sealing engagement therebetween. For example, as the seat 201 may only move along the axis 200 with respect to the valve ball 205, the seat 201 may not be able to move side-to-side and/or rotate with respect to the valve ball 205, such as having the seat 201 move radially with respect to the axis 200. As such, the seat 201 and the valve ball 205 may lose proper sealing engagement therebetween. Though the movement between the valve ball 205 and the seat 201 may be exaggerated and not drawn to scale in FIG. 2B, this type of movement and shifting between the valve ball 205 and the seat 201 may demonstrate how even minor movements may lead to a loss of proper sealing within a valve assembly, particularly within a valve assembly having metal-to-metal seals.
Accordingly, there exists a need to provide a ball valve assembly that may be able to identify and adjust for movements between one or more components within the valve assembly, particularly movement between one or more seats and the valve ball within the valve assembly, without compromising sealing integrity of the valve assembly.